Highly purified toxic fractions from the scorpion centruroides sculpturatus Ewing will be studied on in vitro nerve and muscle preparations using appropriate computer assisted electrophysiologic intracellular and extracellular recording techniques. In addition, isometric twitch tension will be recorded for nerve muscle preparations. Investigations with the crude scorpion venom show probable involvement of the toxins with the excitable sodium conductance system of nerve. Thus, the parameter will be evaluated with standard methods. Also, ions (Na ion, K ion, Ca ions) known to be involved with this system will be varied to reveal involvement of venom fractions with ion systems in the excitable membranes. Also, pharmacologic attempts to reduce venom induced repetitive firing will be conducted. Light and Electron Microscopic evaluation of venom treated preparations will be performed on both isolated nerve and neuromuscular tissues. Both crude venom and selected toxins will be studied.